Re: [Ocfs2-devel] [PATCH 3/4] re-enable "ocfs2: mount shared volume without ha stack" - heming.zhao--- via Ocfs2-devel

From: "heming.zhao--- via Ocfs2-devel" <ocfs2-devel@oss.oracle.com>
To: Mark Fasheh <mark@fasheh.com>
Cc: ocfs2-devel@oss.oracle.com
Subject: Re: [Ocfs2-devel] [PATCH 3/4] re-enable "ocfs2: mount shared volume without ha stack"
Date: Mon, 1 Aug 2022 10:25:46 +0800	[thread overview]
Message-ID: <1719804c-d52c-2015-bcd7-b649bdd56318@suse.com> (raw)
In-Reply-To: <0b33b0c2-71dc-3961-88ee-fb29dedcc7c1@suse.com>

I found I didn't include Joseph in previous mail.

On 8/1/22 09:01, heming.zhao--- via Ocfs2-devel wrote:
> Hello Mark,
> 
> On 8/1/22 01:42, Mark Fasheh wrote:
>> Hi Heming,
>>
>> On Fri, Jul 29, 2022 at 6:15 PM Heming Zhao via Ocfs2-devel
>> <ocfs2-devel@oss.oracle.com> wrote:
>>>
>>> the key different between local mount and non-clustered mount:
>>> local mount feature (tunefs.ocfs2 --fs-features=[no]local) can't do
>>> convert job without ha stack. non-clustered mount feature can run
>>> totally without ha stack.
>>
>> Can you please elaborate on this? Local mounts can run without a
>> cluster stack so I don't see the difference there. We have
> 
> I am using pacemaker cluster stack. In my env, the trouble of the converting between
> local and clustered mounts are only happening on cluster stack.
> 
> the non-clustered mount feature (Gang He commit: 912f655d78c5) gave ocfs2 the ability
> to mount volume at any env (with/without cluster stack).
> The 912f655d78c5 derived from SUSE customer complain: User wanted to fsck the backup
> ocfs2 volume in non-clustered env. They wanted to access the volume quickly and didn't
> want to take time/resource to set up HA stack. (by the way, pcmk stack at least needs
> two nodes to set up a cluster.)

Ooh, above "needs two nodes to set up a cluster" is wrong. User could use a special corosync.conf
to set up a single node cluster. But anyhow, the key is why we can't bypass the setup ha stack
step.

> 
>> tunefs.ocfs2 look for and join the cluster so as to avoid corrupting
>> users data - that's a feature, not a bug. So what I'm seeing here is
>> just opening us to potential corruptions. Is there a specific use case
>> here that you're trying to account for? Are you fixing a particular
>> bug?
>>
> 
> Tunefs.ocfs2 still needs HA/dlm stack to protect joining action. commit 912f655d78c5
> works on non-clustered env, which needs other tech (eg. MMP) to protect corrupting.
> 
>  From my viewpoint, the non-clustered mount code is based on local mount code,
> which gives more flexible than local mount. non-clustered mount uses unify mount
> style align with clustered mount. I think users will like more to use non-clustered
> mount than using tunefs.ocfs2 to change mount type.
> 
> Thanks,
> Heming

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